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avcodec/movtextdec: Simplify checking for invalid extradata

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Every font entry occupies at least three bytes, so checking early
whether there is that much data available is a low-effort way to exclude
invalid extradata. Doing so leads to an overall simplification.

Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit a42695c072)
This commit is contained in:
Andreas Rheinhardt
2020-10-17 13:13:23 +02:00
parent 59b8634411
commit b4a96efdda
1 changed files with 7 additions and 11 deletions
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18
libavcodec/movtextdec.c
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@@ -145,14 +145,13 @@ static void mov_text_cleanup_ftab(MovTextContext *m)
static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m) static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
{ {
uint8_t *tx3g_ptr = avctx->extradata; uint8_t *tx3g_ptr = avctx->extradata;
int i, box_size, font_length; int i, font_length, remaining = avctx->extradata_size - BOX_SIZE_INITIAL;
int8_t v_align, h_align; int8_t v_align, h_align;
unsigned ftab_entries; unsigned ftab_entries;
StyleBox s_default; StyleBox s_default;
m->ftab_entries = 0; m->ftab_entries = 0;
box_size = BOX_SIZE_INITIAL; /* Size till ftab_entries */ if (remaining < 0)
if (avctx->extradata_size < box_size)
return -1; return -1;
// Display Flags // Display Flags
@@ -220,6 +219,9 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
ftab_entries = AV_RB16(tx3g_ptr); ftab_entries = AV_RB16(tx3g_ptr);
if (!ftab_entries) if (!ftab_entries)
return 0; return 0;
remaining -= 3 * ftab_entries;
if (remaining < 0)
return AVERROR_INVALIDDATA;
m->ftab = av_calloc(ftab_entries, sizeof(*m->ftab)); m->ftab = av_calloc(ftab_entries, sizeof(*m->ftab));
if (!m->ftab) if (!m->ftab)
return AVERROR(ENOMEM); return AVERROR(ENOMEM);
@@ -227,18 +229,12 @@ static int mov_text_tx3g(AVCodecContext *avctx, MovTextContext *m)
tx3g_ptr += 2; tx3g_ptr += 2;
for (i = 0; i < m->ftab_entries; i++) { for (i = 0; i < m->ftab_entries; i++) {
box_size += 3;
if (avctx->extradata_size < box_size) {
mov_text_cleanup_ftab(m);
return -1;
}
m->ftab[i].fontID = AV_RB16(tx3g_ptr); m->ftab[i].fontID = AV_RB16(tx3g_ptr);
tx3g_ptr += 2; tx3g_ptr += 2;
font_length = *tx3g_ptr++; font_length = *tx3g_ptr++;
box_size = box_size + font_length; remaining -= font_length;
if (avctx->extradata_size < box_size) { if (remaining < 0) {
mov_text_cleanup_ftab(m); mov_text_cleanup_ftab(m);
return -1; return -1;
} }